Found it for the most part... first fuck her again and again till Sensitivity is maxed out and once more... then there appears a new fuck option. Save the game. You do that and try both. One will have raised "desperation" now.
Then go "masturbate" and "kick her" again and again till desperation is maxed out and once more.
The new fuck option appears again.
After that: spank her pussy and make her cum every time. Now Desperation stays solid and Sensitivity rises again.
Now Desp is maxed, Sens is nearly maxed, but I can't get anything higher anymore.
Normal fuck: "let her cum" rises "Sens" but lowers "desp", "don't let her cum" rises "desp", but lowers "sens". Now take "Let her cum", then go to the poses and there's a new option "degrade". I hope that's it now.
Then regular "fuck" again... Apparently that's it.
No fun... really annoying.